This invention relates to rainshed binders for protecting books, particularly telephone books from environmental conditions such as weather.
Recently, telephone boothes have increased in size to a point where the accompanying telephone book often must be mounted outside a telephone booth for lack of space inside. Accordingly, it has become desirable to provide a binder for protecting such telephone books, particularly when such books are hung vertically from a backbone of the binder wherein the backbone remains in a substantially horizontal position.
As hinges for binders used to protect books, it has been known to use molded polypropylene as a hinge between a backbone of the binder and its covers. Many materials will serve as a hinge if their cross-section is thin enough. However, thin sections in covers usually lack adequate flex life and resistance to vandalizing by tearing. Molded polypropylene is well known for its use as a "miracle hinge." This term usually refers to its extraordinary long hinge flex life. Unfortunately, in thin sections this material is too stiff to be used as a hinge in telephone books. Modified linear polyethylene, on the other hand, is a compromise material which has had good success in typical telephone book binder environments. Modified linear polyethylene is linear polyethylene which is modified by additions to promote flexibility as is well known in the art.
Disregarding toughness and flex life, the use of polypropylene, modified linear polyethylene, or other thermoplastic materials having molded or formed hinges is complicated by the fact that these materials when deformed have poor memories. This causes a book cover, when opened or closed, tend to stay in its last position unless restored by force. Accordingly, a telephone book might be hung downwardly so that covers tend to stay shut. When the book is brought up to a counter and opened by hand, the covers now, however, stay open. When the book is restored to its original position, the covers tend to stay open and only restore to their hang-down position slowly under the force of gravity. Some materials will not restore at all. In these circumstances, the designer is tempted to modify the chemical characteristics of the binder material to obtain a less stiff hinge but in so doing, he may decrease the hinge flex life so much that the usefulness of the book is jeopardized.